1. Field of the Invention
This invention relates to a conjugated diene series rubber composition having an excellent processability at unvulcanized state and excellent rebound resilience, strengths at rupture, particularly high-temperature strength and wear resistance at vulcanized state.
2. Related Art Statement
Recently, the demand on low fuel consumption and safety in automobiles becomes increasingly large. In this connection, the conventional diene series rubber materials can not simultaneously satisfy the low fuel consumption and the safety. Therefore, conjugated diene polymers having excellent rebound resilience and strength at rupture become requested as a rubber material for tires, particularly tire tread and so on.
Heretofore, the conjugated diene polymers having an excellent rebound resilience have been produced by polymerizing butadiene in a hydrocarbon solvent with an organolithium initiator, or by copolymerizing butadiene with an aromatic vinyl compound such as styrene or the like and then reacting with a tin halide or an alkenyltin compound as disclosed in Japanese Patent Application Publication No. 44-4,996, Japanese Patent laid open No. 57-205,414, U.S. Pat. No. 3,956,232 and the like.
In these polymers, however, the strengths at rupture, particularly high-temperature strength are poor, so that severer conditions required in tire tread can not be satisfied.
On the other hand, there are natural rubber, synthetic polyisoprene rubber and so on as a rubber material having excellent strengths at rupture, which are widely used or tire tread in truck and bus under a high loading condition at the present. However, these rubbers are poor in the rebound resilience and wear resistance as compared with the aforementioned butadiene series copolymers obtained by using the organolithium initiator, so that the improvement of these properties are strongly required.